Applicant's invention primarily concerns electrostatic precipitating machines designed for removal of liquid or solid particles of a pollutant found in a flowing gas, such as, for example, particles of smoke found in the gases produced in burning of fossil fuels at a power plant, dusts created during grinding and pulverizing processes, and mists created during the operation of various kinds of chemical processes. Although the primary applications of the invention have to do with control of air pollution, there may as well be other applications of the present invention, in which machines employing electric fields are used to affect the motion of charged particulates flowing in a gas.
Applicant's invention does not itself deal primarily with electrostatic removal of aerosol particulates found in a flowing gas, which is the subject of numerous prior art devices. It is well known in the art that such particles, if electrically charged, may be removed by the application of an electrostatic field directed in a direction generally perpendicular to the gas flow direction, so that the particles may be swept up and collected upon the electrodes used to set up the electric field. For example, the gas may be made to flow between parallel plates across which an electrostatic potential difference is applied, creating an electric field normal to the plates and to the direction of the gas flow. Or the gas may be caused to flow down a cylindrical guide having metal walls and a wire electrode along the axis of the cylinder, and exposed to a radially directed electric field, produced by application of a electrostatic potential difference between the axial electrode and the cylinder wall.
Obviously the efficiency of such electrostatic precipitation machines will be strongly dependent upon the charge state of the particles to be removed. If any significant percentage of these particles remain uncharged while transiting the region of the sweeping electric field, these will escape removal and results will be unsatisfactory, no matter how well designed are the sweeping electrode apparatus and associated components. And for those particles which are charged during transit of the sweeping field region, the sweeping field will obviously be more effective, the greater the average number of charges carried by said particles.
The specific area of applicant's invention is that of apparatus intended to optimize the efficiency of conventional electrostatic precipitator apparatus used in sweeping charged particulates out of a flowing gas, by maximizing the charge state of such particulates before they reach the region of the sweeping electrostatic field.